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Method and a system for filtering tracks originating from several sources and intended for several clients to which they are suppliedMethod and a system for filtering tracks originating from several sources and intended for several clients to which they are supplied description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20090140910, Method and a system for filtering tracks originating from several sources and intended for several clients to which they are supplied. Brief Patent Description - Full Patent Description - Patent Application Claims
The present invention concerns a method and a system for filtering tracks originating from several sources and intended for several clients to which they are supplied, a track containing information relating to an aircraft and a source characterising a type of transmitter. It applies, for example, to the field of avionics. In addition to the voice communications between pilots and air traffic controllers, which are conducted via radio, the increasing development of world civil aviation traffic requires more and more exchanges of formatted information between the systems involved in traffic regulation. For example, the systems exchange data known as tracks, which contain, in particular, kinematical data concerning flying aircrafts, such as position, altitude, bearing and speed. In the civil context, this kinematical data is for the most part deduced from Mode S replies transmitted by the aircrafts themselves and received by ground radars. Mode S replies contain, in particular, aircraft altitude and identifier. On the one hand, the primary radar antennas allow the determination of the successive aircraft positions, managed in a history log, allowing tracks to be deduced. On the other hand, the secondary antennas allow the received altitude and identifier to be assigned to these tracks. We will subsequently refer to the whole set of know tracks as the air picture. New functions implemented on on-board aircraft systems, such as the Airborne Separation Assurance System (ASAS), require on-board knowledge of the air picture. ASAS applications are intended to maintain sufficient aircraft separation, i.e., between tracks and, if appropriate, propose procedures to maintain separation or even procedures to avoid collisions. However, the air picture known to ground centres is limited by the range of radars whose location is a function of the centre\'s needs. This location does not necessarily fulfil the needs of ASAS functions for all aircrafts. Hence, the transmission of the known air picture to aircrafts from the ground is not an appropriate solution. To attempt to resolve this problem, a totally different strategy for the creation of tracks is being implemented, which aims to dispense with the need for ground radars. The first step is to equip aircrafts with a Global Positioning System (GPS), a positioning system based on satellite triangulation. It allows aircrafts to determine their position and altitude very precisely. The history of positions allows very easy deduction of bearing and speed, and to therefore generate their own track themselves. This track is then transmitted to other aircrafts via a new system known as Automatic Dependent Surveillance Broadcast (ADS-B). Aircrafts are equipped with an ADS-B transmitter system to transmit their own track report and an ADS-B receiver system to receive track reports from other aircrafts, at a rate of approximately one per second. These track-type reports are called ADS-B tracks by extension. Aircrafts equipped with an ADS-B transmission and ADS-B reception system have full knowledge of the air picture within the area of coverage of their ADS-B system. Of course, this holds only for the case where all aircrafts are equipped with such ADS-B systems. But this cannot be implemented immediately, given that the current aircraft fleet is not yet equipped with ADS-B, a transitional period must be envisaged. Over this period, aircrafts not equipped with ADS-B can be tracked due to the ability of ADS-B receivers to also receive other track-type reports broadcasted by ground centres to airborne aircrafts via a system called Traffic Information Service in Broadcast mode (TIS-B). This system allows the transmission of reports of various types, including track-type reports, called TIS-B tracks by extension. TIS-B tracks are sent at a rate of about one per second. The position of a TIS-B track is no longer measured by the GPS, but by the ground radars. All aircrafts equipped with and ADS-B receiver system and within range of a TIS-B ground transmission system will receive TIS-B tracks. However, during the transitional period, it should be noted that aircrafts equipped with ADS-B will have incomplete knowledge of the air picture. In effect, an aircraft not equipped with ADS-B that is not within range of a ground radar cannot be tracked. But the on-board knowledge of the air picture is nevertheless more complete than when no aircraft are fitted with ADS-B. Hence, during the transitional period, certain aircrafts have access to tracks originating from TIS-B reports and tracks originating from ADS-B reports. This situation is a potential source of problems. In effect, a ADS-B track and a TIS-B track can result from the same aircraft, which is not at all easy to identify. They are of different origin and therefore often comprise different aircraft identifiers. They will always have differing positions as measured by different systems, i.e., a primary radar antenna and GPS. Not only is it possible that a single aircraft be known by two tracks, but it is also feasible that more than one TIS-B report be sent for the same aircraft by distinct ground stations, depending on the coverage of the TIS-B centres. Hence, a single aircraft may be tracked by three tracks or more. This is why in the rest of the document, we state that a track can be known from several sources, a source characterizing either one of the TIS-B sources or the sole ADS-B track source. In the rest of the document, we will refer to this as a multiple track. Although we may foresee that a pilot will suspect that these multiple tracks originate from the same aircraft due to their excessive spatial proximity, the applications that make use of these tracks cannot make this analysis. This is typically the case for ASAS applications. Schematically, they trigger an alarm when two tracks are too close. Consequently, they cannot work on the basis of multiple tracks for a given aircraft, as these tracks are of course always too close and will therefore be systematically interpreted as distinct aircrafts that are at risk of colliding. The ASAS applications will trigger alerts and propose inappropriate avoidance procedures. But even without considering the specific case of ASAS applications, the existence of several representations for a single aircraft is not an acceptable situation, even for a visualisation application. The transitional period therefore represents a real problem with regard to the integrity of the air picture known on board aircrafts equipped with ADS-B. Some applications are already being used, in particular applications related to in-flight safety, are not able to fulfil their functions under sufficient conditions of reliability. One solution could be to supply a given application with tracks always originating from the same source, TIS-B or ADS-B. In effect, if only those tracks originating from the same source are considered, there will be no multiple tracks for a given aircraft. And, at worst, the air picture supplied to an application originates from a single TIS-B source. This solution is acceptable but it is a pity not to take advantage of ADS-B, which is more complete and precise as based on GPS. The invention has the goal, in particular, of minimising the drawbacks cited above by supplying applications with an air picture that is as complete as possible with the most pertinent tracks, independently of their source of origin. To this end, the invention relates to a filtering of tracks originating from several sources and intended for several clients to which they will be provided. It comprises at least one phase for establishing a link between the tracks resulting from a single aircraft and a phase for selecting one of the linked tracks to represent the aircraft according to a client-dependent criterion, so that a single client may not receive several distinct tracks representing the single aircraft but so that distinct clients may receive distinct tracks representing the single aircraft. Advantageously, the link between the tracks resulting from the single aircraft can be established if the tracks share a same aircraft identifier or if the distance between the tracks is below a separation threshold. Also advantageously, for one of the clients, the track selected from amongst the linked tracks representing the aircraft, may be the track of better quality, for which the probability of being closest to the actual position of the aircraft is the highest. For example, amongst the available track sources, there may be an ADS-B source or a TIS-B source. For one of the clients, the track selected amongst the linked tracks representing the aircraft, can be selected according to an order of preference with regard to the source. One of the principal advantages of the invention is that it allows the air picture to be adapted to the needs of the applications. It is therefore possible to simultaneously supply two distinct applications with different tracks for the same aircraft. For example, an application is exclusively supplied by one source and another application receives only the tracks of best available quality, regardless of their source. Other characteristics and advantages of the invention will be shown through the following description with regard to annexed drawings that represent: Continue reading about Method and a system for filtering tracks originating from several sources and intended for several clients to which they are supplied... Full patent description for Method and a system for filtering tracks originating from several sources and intended for several clients to which they are supplied Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method and a system for filtering tracks originating from several sources and intended for several clients to which they are supplied patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. 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